The present invention relates, in general, to semiconductor processing systems, and more particularly, to improved gas distribution systems for semiconductor processing systems.
Many semiconductor processing systems require the distribution of gas within a processing chamber. For example, in the case of reactive ion etching (RIE), gas is typically distributed inside a low pressure chamber. With RF energy, the gas is converted to a plasma which is capable of etching semiconductor material such as nitrides and oxides, and in some cases metals which have been formed on the semiconductor material.
The semiconductor material within the semiconductor processing system usually takes the form of semiconductor wafers. A parameter of particular concern, during the processing of semiconductor wafers, is the number of microscopic particles which adhere to the wafer during processing. The particles are detrimental to processing because they can prevent the semiconductor device from being properly formed. Consequently, the particles negatively impact yield.
It has been determined that the manner in which gas is distributed in a semiconductor wafer processing system can significantly effect the particle contamination of the semiconductor wafers in the system. In the past, gas has been distributed in the processing system via gas tubes which have pin sized gas inlet holes aligned to and directed generally toward the wafers in the system. It has been determined that gas distributed directly at the wafer increases the probability of particles settling on the wafer. Additionally, in the past, gas inlet holes of adjacent gas tubes within the system have been located in opposing positions, causing a resultant gas flow which is directed toward the wafers. It has been determined that this condition also increases the probability of particles adhering to the wafers.
An additional problem presenting itself in the conventional gas distribution system is the difficulty of cleaning the gas tubes. In the past, the gas tubes have had a cap permanently fixed to one end. Consequently, nothing could be passed completely through the tube for cleaning. Furthermore, it is impossible to see into the tube for cleaning.
What is needed is an improved gas distribution system which causes gas to flow in an optimal configuration in order to minimize the number of particles settling on the semiconductor wafer surface. Additionally, it would be desirable to provide gas tubes which are easily cleaned. Furthermore, it would be desirable to provide a gas tube which can be conveniently installed in the system so that gas inlets are properly aligned.